The present invention relates in general to pulse oximetry, and in particular to the processing of signals generated by a pulse oximeter.
A pulse oximeter is typically used to measure various blood characteristics including the blood oxygen saturation of hemoglobin in arterial blood and the pulse rate of the patient. Measurement of these characteristics has been accomplished by use of a non-invasive sensor that passes light through a portion of a patient's blood perfused tissue and photo-electrically senses the absorption and scattering of light in such tissue. The amount of light absorbed and scattered is then used to estimate the amount of blood constituent in the tissue using various algorithms known in the art. The “pulse” in pulse oximetry comes from the time varying amount of arterial blood in the tissue during a cardiac cycle. The signal processed from the sensed optical measurement is the familiar plethysmographic waveform, which corresponds with the cyclic attenuation of optical energy through a portion of a patient's blood perfused tissue.
Various physiological and/or external factors can adversely impact the accuracy and/or the reliability of physiological parameters that are estimated by a pulse oximeter. These undesirable factors are sometimes referred to as artifacts. Venous pulsation is one undesired artifact in pulse oximetry, and may be caused by a patient's medical condition.
It is therefore desirable that a pulse oximetry system be designed which effectively and accurately detects and/or notifies a clinician of the presence of venous pulsation.